Angle detection device

ABSTRACT

There has been a problem that a rotation second-order angle error due to a phase difference between a sine signal and a cosine signal deviating from π/2 cannot be reduced. Therefore, provided is an angle detection device that can suppress a second-order angle error caused due to the phase difference between a first sine signal and a second sine signal deviating from π/2, by calculating a detection angle from a first detection signal based on the sum of two sine signals having different phases and a second detection signal based on the difference of the two sine signals.

TECHNICAL FIELD

The present disclosure relates to an angle detection device.

BACKGROUND ART

In order to provide a motor having reduced torque ripple, detectionaccuracy of rotation position of a rotor is required to be improved. Inthe electric power steering control device of Patent Document 1, adetection signal is corrected using a midpoint correction value, of asine signal and a cosine signal of a resolver, stored in an EEPROM(Electrically Erasable Programmable Read-Only-Memory) or the like inadvance, whereby a rotation first-order angle error caused due to arotation 0-order signal error is reduced. In addition, the sine signaland the cosine signal of the resolver that have been subjected to themidpoint correction are multiplied, to be corrected, by an amplitudecorrection coefficient stored in an EEPROM or the like in advance,whereby a rotation second-order angle error caused due to a rotationfirst-order signal error is reduced (see Patent Document 1, forexample).

CITATION LIST Patent Document

-   Patent Document 1: Japanese Laid-Open Patent Publication No.    2008-273478

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

When the method according to Patent Document 1 is used, a rotationfirst-order angle error caused due to an offset error included in a sinesignal and a cosine signal, or a rotation second-order angle errorcaused due to an amplitude ratio can be reduced. However, a rotationsecond-order angle error due to a phase difference between the sinesignal and the cosine signal deviating from π/2 cannot be reduced.

The present disclosure has been made in order to solve the aboveproblem. An object of the present disclosure is to provide an angledetection device that can reduce a rotation second-order angle error dueto the phase difference between a sine signal and a cosine signaldeviating from π/2.

Solution to the Problems

An angle detection device according to the present disclosure includes:

an angle detector for detecting a first sine signal and a second sinesignal having a phase different from that of the first sine signal, inaccordance with rotation of a rotating machine;

a detection signal calculation unit for outputting a first detectionsignal based on a sum of the first sine signal and the second sinesignal, and a second detection signal based on a difference between thefirst sine signal and the second sine signal; and

an angle calculation unit for calculating a detection angle on the basisof the first detection signal and the second detection signal, wherein

a second-order angle error caused due to a phase difference between thefirst sine signal and the second sine signal deviating from π/2 issuppressed.

Effect of the Invention

According to the angle detection device of the present disclosure, adetection angle is calculated using the sum and the difference of twosine signals having different phases, whereby occurrence of a rotationsecond-order angle error due to the phase difference between the twosine signals can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a positional relationship betweenan angle detector and a sensor magnet according to embodiment 1. FIG. 1Ais a top view and FIG. 1B is a side view.

FIG. 2 is a block configuration diagram showing a configuration of anangle detection device in embodiment 1.

FIG. 3 shows an example of hardware of a detection signal calculationunit and an angle calculation unit in embodiment 1.

FIG. 4 shows angle error when a detection angle θ is obtained based on afirst sine signal and a second sine signal. In FIG. 4A, the horizontalaxis represents sensor angle. In FIG. 4B, the horizontal axis representsorder number.

FIG. 5 shows error of detection angle obtained when 0 to 5 V issubjected to A/D conversion at a 10 bit resolution in a case where thephase difference is −π/3.

FIG. 6 shows error of detection angle obtained when 0 to 5 V issubjected to A/D conversion at a 10 bit resolution in a case where thephase difference is −π/6.

FIG. 7 shows a first sine signal and a second sine signal, and a firstdetection signal and a second detection signal in terms of a vectordiagram.

FIG. 8 is a block configuration diagram showing a configuration of anangle detection device according to embodiment 3.

FIG. 9 shows a normal range of an angle detection device in one cycle ofsensor angle when the phase difference between the first sine signal andthe second sine signal is π/2.

FIG. 10 shows a normal range of the angle detection device in one cycleof sensor angle when the phase difference between the first sine signaland the second sine signal is π/3.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a suitable embodiment of a power control device accordingto the present disclosure will be described with reference to thedrawings. It is noted that the same components and corresponding partsare denoted by the same reference characters, and the detaileddescription thereof is omitted. Also, in the other embodiments,components denoted by the same reference characters will not berepeatedly described.

Embodiment 1

Examples of an angle detector 1 used in an angle detection device of thepresent disclosure include a resolver, a sensor using amagneto-resistive element (MR sensor), an encoder, a Hall element, andthe like. Since similar effects can be obtained in each case,description herein is given using an MR sensor as an example.

FIG. 1 is a schematic diagram showing a positional relationship betweenthe angle detector 1 and a sensor magnet 10 according to embodiment 1.FIG. 1A is a top view and FIG. 1B is a side view. The angle detector 1detects a magnetic field generated by the sensor magnet 10, and outputsa first sine signal V sin 1 and a second sine signal V sin 2. Since thesensor magnet 10 rotates together with a rotor (not shown), the magneticfield generated in the angle detector 1 by the sensor magnet 10 changesin accordance with an angle.

FIG. 2 is a block configuration diagram showing a configuration of theangle detection device in embodiment 1 of the present disclosure. Theangle detector 1 outputs the first sine signal V sin 1 and the secondsine signal V sin 2 on the basis of the magnetic field, of the sensormagnet 10, that changes in accordance with the angle of the rotor. Thefirst sine signal V sin 1 and the second sine signal V sin 2 are sinewaves having different phases represented by formula (1) below. θsrepresents a sensor angle, a1 represents an amplitude, γ represents aphase difference, and Vc represents a DC voltage supplied to the angledetector. Here, the amplitude ratio between the first sine signal V sin1 and the second sine signal V sin 2 is 1. However, when the amplitudeis different, correction may be performed such that the amplitude ratiobecomes 1.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 1} \right\rbrack & \; \\\left\{ \begin{matrix}{V_{\sin 1} = {{a_{1}{cos\theta}_{s}} + {V_{c}/2}}} \\{V_{\sin 2} = {{a_{1}{\cos\left( {\theta_{s} + \gamma} \right)}} + {V_{c}/2}}}\end{matrix} \right. & (1)\end{matrix}$

A detection signal calculation unit 2 outputs a first detection signal Vsin_det1 and a second detection signal V sin_det2 according to formula(2), using the first sine signal V sin 1 and the second sine signal Vsin 2 obtained by the angle detector 1. The first detection signal Vsin_det1 is obtained by subtracting a DC voltage Vc supplied to theangle detector, from the sum of the first sine signal V sin 1 and thesecond sine signal V sin 2.

The second detection signal V sin_det2 is obtained by subtracting thesecond sine signal V sin 2 from the first sine signal V sin 1. Here, asa subtraction term for reducing an angle error due to a so-called phasedifference deviation, a value that is twice Vc/2, which is the midpointvoltage of the first sine signal V sin 1, i.e., the DC voltage Vcsupplied to the angle detector, is used. However, when the midpointvoltage is not Vc/2, if a value that suits such a case is used, similareffects can be obtained. When variations are caused due to environmentaltemperature, aged deterioration, and the like, a value in considerationof such variations may be used. This value may be set or updated online.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 2} \right\rbrack & \; \\\left\{ \begin{matrix}{V_{{si}\; n\;\_\;\det\; 1} = {{V_{{si}\; n\; 1} + V_{{si}\; n\; 2} - V_{c}} = {\sqrt{2}\sqrt{1 + {\cos\;\gamma}}a_{1}{\cos\left( {\theta_{s} - \xi_{1}} \right)}}}} \\{V_{{si}\; n\;\_\;\det\; 2} = {{V_{{si}\; n\; 1} - V_{{si}\; n\; 2}} = {\sqrt{2}\sqrt{1 - {\cos\;\gamma}}a_{1}{\cos\left( {\theta_{s} - \xi_{1}} \right)}}}}\end{matrix} \right. & (2)\end{matrix}$

ξ1 and ξ2 satisfy formula (3), and the phase difference is π/2.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 3} \right\rbrack & \; \\\left\{ \begin{matrix}{\xi_{1} = {{\tan^{- 1}\left( \frac{\sin\;\gamma}{1 + {\cos\;\gamma}} \right)} = \frac{\gamma}{2}}} \\{\xi_{2} = {{\tan^{- 1}\left( \frac{{- \sin}\;\gamma}{1 - {\cos\;\gamma}} \right)} = {\frac{\pi}{2} + \frac{\gamma}{2}}}}\end{matrix} \right. & (3)\end{matrix}$

That is, regardless of the value of the phase difference γ between thefirst sine signal V sin 1 and the second sine signal V sin 2, which areoriginal signals, the first detection signal V sin_det1 and the seconddetection signal V sin_det2 for which orthogonality is ensured can beobtained by the detection signal calculation unit 2.

An angle calculation unit 3 calculates a detection angle θ as in formula(4), for example, using the first detection signal V sin_det1 and thesecond detection signal V sin_det2 obtained by the detection signalcalculation unit 2. Here, the detection angle θ is described in terms ofa formula, but the detection angle θ may be calculated using aconversion table defined in advance. When the output result of thedetection signal calculation unit 2 is used, the zero point deviatesfrom the original zero point as shown in formula (3). Here, whencorrection is performed by π/2+γ/2, it is possible to obtain the samezero point as that based on the angle calculated from the first sinesignal V sin 1 and the second sine signal V sin 2.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 4} \right\rbrack & \; \\{\theta = {{\tan^{- 1}\left( {k\frac{V_{{si}\; n\;\_\;\det\; 1}}{V_{{si}\; n\;\_\;\det\; 2}}} \right)} - \left( {\frac{\pi}{2} + \frac{\gamma}{2}} \right)}} & (4)\end{matrix}$

A coefficient k may be given according to formula (5) in considerationof the amplitude ratio in formula (2). Accordingly, a second-order angleerror due to amplitude deviation can be reduced. In formula (4), a valueobtained by multiplying the ratio between the first detection signal Vsin_det1 and the second detection signal V sin_det2 by the coefficient kis applied in an inverse tangent function. However, either one of thefirst detection signal V sin_det1 and the second detection signal Vsin_det2 may be multiplied by a coefficient corresponding to theamplitude ratio.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 5} \right\rbrack & \; \\{k = \sqrt{\frac{1 - {\cos\;\gamma}}{1 + {\cos\;\gamma}}}} & (5)\end{matrix}$

FIG. 3 shows an example of hardware of the detection signal calculationunit 2 and the angle calculation unit 3. The hardware is composed of aprocessor 100 and a storage device 101. Although not shown, the storagedevice includes a volatile storage device such as a random access memoryand a nonvolatile auxiliary storage device such as a flash memory.Instead of the flash memory, a hard disk as an auxiliary storage devicemay be provided. By executing a program inputted from the storage device101, the processor 100 performs detection signal calculation or anglecalculation described above, for example. In this case, a program isinputted to the processor 100 from the auxiliary storage device via thevolatile storage device. The processor 100 may output data such as acalculation result to the volatile storage device of the storage device101, or may store the data in the auxiliary storage device via thevolatile storage device.

Next, as a specific example, effects of the present embodiment 1 whenthe phase difference γ between the first sine signal V sin 1 and thesecond sine signal V sin 2 is −π/3 are described. In this case, formula(1) becomes formula (6). As in formula (7), when the detection angle θis obtained on the basis of the first sine signal V sin 1 and the secondsine signal V sin 2, the angle error is in 0-order and 2n-ordercomponents as shown in FIG. 4.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 6} \right\rbrack & \; \\\left\{ \begin{matrix}{V_{{si}\; n\; 1} = {{a_{1}\cos\;\theta_{s}} + \frac{V_{c}}{2}}} \\{V_{{si}\; n\; 2} = {{a_{1}{\cos\left( {\theta_{2} - \frac{\pi}{3}} \right)}} + \frac{V_{c}}{2}}}\end{matrix} \right. & (6) \\\left\lbrack {{Math}.\mspace{14mu} 7} \right\rbrack & \; \\{\theta = {\tan^{- 1}\left( \frac{V_{{si}\; n\; 2} - \frac{V_{c}}{2}}{V_{{si}\; n\; 1} - \frac{V_{c}}{2}} \right)}} & (7)\end{matrix}$

In contrast, in the case of the angle detection device of the presentembodiment 1, the first detection signal V sin_det1 and the seconddetection signal V sin_det2 are obtained by the detection signalcalculation unit 2 as represented by formula (8).

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 8} \right\rbrack & \; \\\left\{ \begin{matrix}{V_{{si}\; n\;\_\;\det\; 1} = {\sqrt{3}a_{1}{\cos\left( {\theta_{s} - \frac{\pi}{6}} \right)}}} \\{V_{{si}\; n\;\_\;\det\; 2} = {a_{1}{\cos\left( {\theta_{s} - \frac{\pi}{3}} \right)}}}\end{matrix} \right. & (8)\end{matrix}$

The detection angle θ can be calculated by the angle calculation unit 3according to formula (9) in which the amplitude ratio and the zero pointdeviation have been adjusted. That is, even in a case where the phasedifference between the first sine signal V sin 1 and the second sinesignal V sin 2 is not ±π/2, when an angle is calculated using the firstdetection signal V sin_det1 and the second detection signal V sin_det2for which orthogonality is ensured, a sensor angle second-order angleerror caused due to the phase difference deviating from π/2 can besuppressed.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 9} \right\rbrack & \; \\{\theta = {{{\tan^{- 1}\left( \frac{\sqrt{3}V_{{si}\; n\;\_\;\det\; 2}}{V_{{si}\; n\;\_\;\det\; 1}} \right)} - \frac{\pi}{6}} \approx \theta_{s}}} & (9)\end{matrix}$

Meanwhile, in many cases, the first sine signal V sin 1 and the secondsine signal V sin 2 obtained from the angle detector are subjected toA/D conversion, to be used. For example, when 0 to 5 V is subjected toconversion at a 10 bit resolution, the minimum resolution is about 4.9mV. When formula (6) and formula (8) are compared with each other, theamplitudes of the original signals is a1, whereas the amplitudes of thesignals calculated using the sum and the difference are √3a1 and a1.

FIG. 5 shows error of the detection angle θ (sensor angle) obtained when0 to 5 V is subjected to A/D conversion at a 10 bit resolution in a casewhere the amplitudes of the first detection signal V sin_det1 and thesecond detection signal V sin_det2 are both 2 V, and the phasedifference γ therebetween is −π/3.

FIG. 6 shows error of the detection angle θ (sensor angle) obtained when0 to 5 V is subjected to A/D conversion at a 10 bit resolution in a casewhere the amplitudes of the first detection signal V sin_det1 and thesecond detection signal V sin_det2 are both 2 V and the phase differenceγ therebetween is −π/6. When the phase difference γ is −π/6 as in FIG.6, the amplitude of the second detection signal V sin_det2 is smallerthan the amplitude of the first sine signal V sin 1 and the second sinesignal V sin 2, which are the original signals, whereby the accuracydecreases, and accordingly, the angle error increases.

A condition for the amplitudes of the first detection signal and thesecond detection signals to be both greater than or equal to theamplitudes of the original signals is formula (9-1), on the basis offormula (1) and formula (2).

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 10} \right\rbrack & \; \\\left\{ \begin{matrix}{{\sqrt{2}\sqrt{1 + {\cos\;\gamma}}} \geq 1} \\{{\sqrt{2}\sqrt{1 - {\cos\;\gamma}}} \geq 1}\end{matrix} \right. & \left( {9\text{-}1} \right)\end{matrix}$

When this is solved, formula (9-2) is obtained.

[Math. 11]

−½≤cos γ≤½  (9-2)

That is, when the phase difference between the first sine signal V sin 1and the second sine signal V sin 2 is not less than π/3 and not greaterthan ⅔π, the amplitudes of the first detection signal V sin_det1 and thesecond detection signal V sin_det2 are prevented from becoming smallerthan those of the first sine signal V sin 1 and the second sine signal Vsin 2, which are the original signals. Accordingly, decrease in accuracydue to the resolution of A/D conversion can be suppressed. This is aneffect that has not been realized in conventional art.

When this is expressed by vectors as shown FIG. 7, changes in theamplitude and the phase are easily understood. The first sine signal Vsin 1 and the second sine signal V sin 2 are vectors whose phases aredifferent by π/3. Therefore, the second detection signal V sin_det2,which is the difference between the vectors, is a side of an equilateraltriangle. This has a magnitude equal to those of the vectors of thefirst sine signal V sin 1 and the second sine signal V sin 2, which arethe original signals. When the phase difference between the first sinesignal V sin 1 and the second sine signal V sin 2 is smaller than π/3,the amplitude of the first detection signal V sin_det1 represented bythe sum of the first sine signal V sin 1 and the second sine signal Vsin 2 increases, whereas the amplitude of the second detection signal Vsin_det2 represented as the difference between the first sine signal Vsin 1 and the second sine signal V sin 2 decreases.

When the phase difference between the first sine signal V sin 1 and thesecond sine signal V sin 2 is greater than π/3, the amplitude of thefirst detection signal V sin_det1 represented by the sum of the firstsine signal V sin 1 and the second sine signal V sin 2 becomes smallerthan when the phase difference is π/3, but is greater than theamplitudes of the first sine signal V sin 1 and the second sine signal Vsin 2, which are the original signals, whereas the amplitude of thesecond detection signal V sin_det2 represented by the difference betweenthe first sine signal V sin 1 and the second sine signal V sin 2 becomesgreater than when the phase difference is π/3, and becomes greater thanthe amplitudes of the first sine signal V sin 1 and the second sinesignal V sin 2, which are the original signals.

When the phase difference between the first sine signal V sin 1 and thesecond sine signal V sin 2 is π/2, the amplitude of the first detectionsignal V sin_det1 and the amplitude of the second detection signal Vsin_det2 become equal to each other. Further, when the phase differencebetween the first sine signal V sin 1 and the second sine signal V sin 2is greater than π/2, the amplitude of the second detection signal Vsin_det2 represented by the difference between the first sine signal Vsin 1 and the second sine signal V sin 2 becomes further greater,whereas the amplitude of the first detection signal V sin_det1represented by the sum of the first sine signal V sin 1 and the secondsine signal V sin 2 becomes further smaller.

Then, when the phase difference exceeds ⅔π, the amplitude of the firstdetection signal V sin_det1 becomes smaller than those of the first sinesignal V sin 1 and the second sine signal V sin 2, which are theoriginal signals.

In formula (4) above, description has been given without taking an errordue to fixed-point calculation into consideration. When multiplicationof a correction coefficient is performed such that a signal having alarge amplitude suits the amplitude of a signal having a smallamplitude, cancellation of significant digits occurs and the accuracy isdeteriorated. When correction is performed by multiplying the signalhaving the smaller amplitude by a correction coefficient that is notless than 1 based on the amplitude ratio, an angle error due toamplitude deviation can be reduced while preventing deterioration of theaccuracy caused when multiplication by a correction coefficient isperformed.

When the phase difference is π/3 or ⅔π, the amplitude of either thefirst detection signal V sin_det1 or the second detection signal Vsin_det2 becomes equal to the amplitudes of the first sine signal V sin1 and the second sine signal V sin 2, which are the original signals.Therefore, decrease in accuracy due to the resolution of A/D conversioncaused by decrease in amplitude can be suppressed. Although the phasedifference between the first sine signal V sin 1 and the second sinesignal V sin 2, which are the original signals, is greatly deviated fromπ/2, when the angle calculation method based on the first detectionsignal and the second detection signal having orthogonality described inthe present embodiment is used, the second-order angle error caused dueto the phase difference deviation can be reduced by a simpleconfiguration. For example, when the phase difference between the firstsine signal V sin 1 and the second sine signal V sin 2 is π/3 as shownin FIG. 7, the second detection signal having the smaller amplitude maybe multiplied by a correction coefficient that is not less than 1.

Embodiment 2

When the phase difference is π/2, the amplitudes of the first detectionsignal V sin_det1 and the second detection signal V sin_det2 are both √2times the amplitudes of the first sine signal V sin 1 and the secondsine signal V sin 2, which are the original signals. Therefore, decreasein accuracy due to the resolution of A/D conversion can be suppressed,and at the same time, the phase difference deviation of the first sinesignal V sin 1 and the second sine signal V sin 2, which are theoriginal signals, can be replaced with an amplitude ratio deviation ofthe first detection signal V sin_det1 and the second detection signal Vsin_det2. This effect is described with reference to an example casewhere the first sine signal V sin 1 and the second sine signal V sin 2are given as in formula (10).

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 12} \right\rbrack & \; \\\left\{ \begin{matrix}{V_{{si}\; n\; 1} = {a_{0} + {a_{1}\cos\;\theta_{s}}}} \\{V_{{si}\; n\; 2} = {c_{0} + {c_{1}\cos\;\theta_{s}} + {d_{1}\sin\;\theta_{s}}}}\end{matrix} \right. & (10)\end{matrix}$

Although the amplitude of the first sine signal V sin 1 is a1, theamplitude of the second sine signal V sin 2 is

√{square root over (c ₁ ² +d ₁ ²)}  [Math. 13]

and thus, the amplitude ratio is not 1. In this state, when the firstdetection signal V sin_det1 and the second detection signal V sin_det2are calculated, the phase difference between the two signals is deviatedfrom π/2.

The amplitude of the first detection signal V sin_det1 can be calculatedby, for example, subtracting the minimum value of the signal from themaximum value thereof and dividing the resultant value by 2. An offseta0 can be calculated by using, for example, the average value in onecycle of the signal or the average of the maximum value and the minimumvalue of the signal. Similarly, the amplitude of the second detectionsignal V sin_det2 can be calculated by, for example, subtracting theminimum value of the signal from the maximum value thereof, and dividingthe resultant value by 2. An offset c0 can be calculated by using, forexample, the average value in one cycle of the signal or the average ofthe maximum value and the minimum value of the signal. When theamplitude ratio is not 1, or when the offsets of the two signals aredifferent, correction according to formula (11) may be performed in thedetection signal calculation unit 2. Accordingly, the first-order angleerror due to the offset error can be reduced. Even when the offset a0and the offset c0 are not very small values, such as Vc/2 in formula(1), the offsets are adjusted before the amplitude correction, and thus,the first order angle error can be suppressed.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 14} \right\rbrack & \; \\\left\{ \begin{matrix}{V_{{si}\; n\; 1\_\;{hosei}} = {\frac{\sqrt{c_{1}^{2} + d_{1}^{2}}}{a_{1}}\left( {V_{{si}\; n\; 1} - a_{0}} \right)}} \\{V_{{si}\; n\; 2\_\;{hosei}} = {V_{{si}\; n\; 2} - c_{0}}}\end{matrix} \right. & (11)\end{matrix}$

When the first detection signal V sin_det1 and the second detectionsignal V sin_det2 are calculated in formula (12) using correctionsignals V sin 1_hosei and V sin 2_hosei calculated in formula (11), twosignals of which the phase difference is π/2 can be obtained.

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 15} \right\rbrack & \; \\\left\{ \begin{matrix}{V_{{si}\; n\;\_\;\det\; 1} = {V_{{si}\; n\; 1\_\;{hosei}} + V_{{si}\; n\; 2\_\;{hosei}}}} \\{V_{{si}\; n\;\_\;\det\; 2} = {V_{{si}\; n\; 1\_\;{hosei}} - V_{{si}\; n\; 2\_\;{hosei}}}}\end{matrix} \right. & (12)\end{matrix}$

Since the amplitude ratio between the first detection signal V sin_det1and the second detection signal V sin_det2 is not 1, if the ratiobetween the amplitude obtained by subtracting the minimum value of thefirst detection signal V sin_det1 from the maximum value thereof and theamplitude obtained by subtracting the minimum value of the seconddetection signal V sin_det2 from the maximum value thereof is used asthe coefficient k of formula (4), correction can be performed when thedetection angle θ is calculated in the angle calculation unit 3.Accordingly, the second-order angle error can be suppressed.

When the phase difference is corrected, the phase difference needs to becalculated from the relationship between two signals. Thus, the phasedifference is difficult to be calculated using a single signal.Meanwhile, when the amplitude is corrected, the amplitude can beobtained from each signal. Thus, the correction value can be easilyupdated online, and is not limited to using adjustment values written inan EEPROM in advance.

In formula (11) and formula (12), the offsets are corrected using thefirst sine signal V sin 1 and the second sine signal V sin 2. However,the offsets may be corrected using the first detection signal V sin_det1and the second detection signal V sin_det2. In this case, the amplituderatio between the first sine signal V sin 1 and the second sine signal Vsin 2 is set to 1 in formula (13). At this time, the offset a0 of thefirst sine signal V sin 1 is multiplied by a correction coefficient, butthe product of error can be approximated to be very small as in formula(14).

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 16} \right\rbrack & \; \\\left\{ \begin{matrix}{V_{{si}\; n\; 1\_\;{hosei}} = {\frac{\sqrt{c_{1}^{2} + d_{1}^{2}}}{a_{1}}V_{{si}\; n\; 1}}} \\{V_{{si}\; n\; 2\_\;{hosei}} = V_{{si}\; n\; 2}}\end{matrix} \right. & (13) \\\left\lbrack {{Math}.\mspace{14mu} 17} \right\rbrack & \; \\\begin{matrix}{V_{{si}\; n\; 1\_\;{hosei}} = {{\frac{\sqrt{c_{1}^{2} + d_{1}^{2}}}{a_{1}}a_{1}\cos\;\theta_{s}} - {\left\{ {1 + \left( {\frac{\sqrt{c_{1}^{2} + d_{1}^{2}}}{a_{1}} - 1} \right)} \right\} a_{0}}}} \\{\approx {{\frac{\sqrt{c_{1}^{2} + d_{1}^{2}}}{a_{1}}a_{1}\cos\;\theta_{s}} - a_{0}}}\end{matrix} & (14)\end{matrix}$

Therefore, with respect to the first detection signal V sin_det1 and thesecond detection signal V sin_det2, the offsets can be correctedaccording to formula (15).

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 18} \right\rbrack & \; \\\left\{ \begin{matrix}{V_{{si}\; n\;\_\;\det\; 1} = {V_{{si}\; n\; 1\_\;{hosei}} + V_{{si}\; n\; 2\_\;{hosei}} - \left( {a_{0} + c_{0}} \right)}} \\{V_{{si}\; n\;\_\;\det\; 2} = {V_{{si}\; n\; 1\_\;{hosei}} - V_{{si}\; n\; 2\_\;{hosei}} - \left( {a_{0} - c_{0}} \right)}}\end{matrix} \right. & (15)\end{matrix}$

Here, the effects of offset correction and amplitude ratio correctionhave been described in a case where the phase difference is π/2.However, it is understood that the same effects can also be obtained ina case where the phase difference has another value.

Embodiment 3

In embodiment 1 above, description has been given for a method forsuppressing the second-order angle error caused due to a phasedifference deviation of the first sine signal V sin 1 and the secondsine signal V sin 2, by calculating a detection angle by using the firstdetection signal V sin_det1 obtained from the sum of the first sinesignal V sin 1 and the second sine signal V sin 2 and the seconddetection signal V sin_det2 obtained from the difference between thefirst sine signal V sin 1 and the second sine signal V sin 2. In thepresent embodiment 3, a failure determination method is described.

FIG. 8 is a block configuration diagram showing a configuration of anangle detection device in the present embodiment 3. A failure determiner4 is added to FIG. 2. The failure determiner 4 determines a failureusing a sum of squares or a square root of sum of squares of the firstdetection signal V sin_det1 and the second detection signal V sin_det2.In the following, determination using the sum of squares is described,but the same effect can be obtained also in the case of the square rootof sum of squares. Similar to embodiment 1, the hardware of the failuredeterminer may be composed of the processor 100 and the storage device101.

In a case where the phase difference between the first sine signal V sin1 and the second sine signal V sin 2 is π/2, when the horizontal axisrepresents the first sine signal V sin 1 and the vertical axisrepresents the second sine signal V sin 2, a circular trajectoryindicated by a broken line as in FIG. 9 is ideally realized in one cycleof sensor angle. Since the amplitude of each signal is changed due totemperature or varies due to aged deterioration, the hatched area isdefined as a normal range P, and being outside the normal range P isdetermined as a failure. The radius of the inner circle represents alower limit threshold, the radius of the outer circle represents anupper limit threshold, and a star mark represents a state immediatelybefore a failure. When an abnormality has occurred in a sine wavesignal, the sine wave signal changes within the range indicated by anarrow. The range indicated by the arrow has a portion that is outsidethe hatched part, and a failure is determined in this portion. Thismethod uses a feature that, when the orthogonality between two signalsis ensured, the sum of squares is constant. However, when the phasedifference is not π/2, for example, the phase difference is π/3, aslanted ellipsoid trajectory is obtained as shown in FIG. 10. Withrespect to the slanted ellipsoid trajectory, when a normal range Q isset in consideration of change in temperature and variation due to ageddeterioration, a significantly larger range when compared with that inFIG. 9 is obtained. This causes a situation where a failure cannot bedetermined even when a failure should be determined.

A case where the first sine signal V sin 1 and the second sine signal Vsin 2 are given by formula (6) described in embodiment 1 is described.According to formula (6), a sum of squares Vsum of the first sine signaland the second sine signal varies at the sensor angle second order as informula (16).

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 19} \right\rbrack & \; \\{V_{sum} = {{\left( {V_{{si}\; n\; 1} - \frac{V_{c}}{2}} \right)^{2} + \left( {V_{{si}\; n\; 2} - \frac{V_{c}}{2}} \right)^{2}} = {\frac{a_{1}^{2}}{2}\left\{ {2 + {\cos\left( {{2\theta_{s}} - \frac{\pi}{3}} \right)}} \right\}}}} & (16)\end{matrix}$

When the sum of squares Vsum is calculated using the first detectionsignal V sin_det1 and the second detection signal V sin_det2 in formula(8), the sum of squares Vsum varies at the sensor angle second order asin formula (17).

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 20} \right\rbrack & \; \\{V_{sum} = {{V_{{{si}\; n\; 1\;\_\;\det}\;}^{2} + V_{{{si}\; n\; 2\;\_\;\det}\;}^{2}} = {a_{1}^{2}\left\{ {2 + {\cos\left( {{2\theta_{s}} - \frac{\pi}{3}} \right)}} \right\}}}} & (17)\end{matrix}$

The variation component in formula (16) is caused because the phasedifference between the first sine signal V sin 1 and the second sinesignal V sin 2 is not π/2, whereas the variation component in formula(17) is caused because the amplitudes of the first detection signal Vsin_det1 and the second detection signal V sin_det2 are different. Inorder to suppress the variation component in formula (16), the phaseneeds to be changed. However, in order to suppress the variationcomponent in formula (17), the amplitude only needs to be adjusted as informula (18).

[Math. 21]

V _(sum) =V _(sin1_det) ²+(√{square root over (3)}V _(sin2_det))²=3a ₁²  (18)

That is, regardless of the phase difference between the first sinesignal V sin 1 and the second sine signal V sin 2, if the amplitude ofat least one of the first detection signal V sin_det1 or the seconddetection signal V sin_det2 is corrected and the sum of squares iscalculated, a circular trajectory when the phase difference is π/2 as inFIG. 9 can be obtained to be used in failure determination. This is aneffect that has not been realized in conventional art. This eliminatesthe need of taking deviation due to phase difference into consideration,and thus, facilitates designing of a determination threshold.

Although the present disclosure is described above in terms of variousexemplary embodiments and implementations, it should be understood thatthe various features, aspects, and functionality described in one ormore of the individual embodiments are not limited in theirapplicability to the particular embodiment with which they aredescribed, but instead can be applied, alone or in various combinationsto one or more of the embodiments of the disclosure.

It is therefore understood that numerous modifications which have notbeen exemplified can be devised without departing from the scope of thepresent disclosure. For example, at least one of the constituentcomponents may be modified, added, or eliminated. At least one of theconstituent components mentioned in at least one of the preferredembodiments may be selected and combined with the constituent componentsmentioned in another preferred embodiment.

DESCRIPTION OF THE REFERENCE CHARACTERS

-   -   1 angle detector    -   2 detection signal calculation unit    -   3 angle calculation unit    -   4 failure determiner    -   100 processor    -   101 storage device

1. An angle detection device comprising: an angle detector for detectinga first sine signal and a second sine signal having a phase differentfrom that of the first sine signal, in accordance with rotation of arotating machine; a detection signal calculator to output a firstdetection signal based on a sum of the first sine signal and the secondsine signal, and a second detection signal based on a difference betweenthe first sine signal and the second sine signal; and an anglecalculator to calculate a detection angle on the basis of the firstdetection signal and the second detection signal, wherein a second-orderangle error caused due to a phase difference between the first sinesignal and the second sine signal deviating from π/2 is suppressed. 2.The angle detection device according to claim 1, wherein the firstdetection signal is calculated by subtracting a value determined inadvance from the sum of the first sine signal and the second sinesignal.
 3. The angle detection device according to claim 2, wherein thevalue determined in advance is twice a midpoint potential of the firstsine signal.
 4. The angle detection device according to claim 2, whereinthe value determined in advance is a DC voltage supplied to the angledetector.
 5. The angle detection device according to claim 2, whereinthe value determined in advance is capable of being set online.
 6. Theangle detection device according to claim 1, wherein an angle detectionvalue calculated in the angle calculator is calculated by subtracting,from an angle obtained through an inverse tangent function of a ratiobetween the first detection signal and the second detection signal, avalue that is ½ of the phase difference between the first sine signaland the second sine signal, or a value obtained by adding π/2 to ½ ofthe phase difference between the first sine signal and the second sinesignal.
 7. The angle detection device according to claim 1, wherein atleast one of the first sine signal or the second sine signal iscorrected such that an amplitude ratio between the first sine signal andthe second sine signal is
 1. 8. The angle detection device according toclaim 1, wherein the first sine signal is corrected through subtractionof a first offset correction value, and the second sine signal iscorrected through subtraction of a second offset correction value. 9.The angle detection device according to claim 1, further comprising afailure determiner to determine a failure of the angle detector, whereinthe failure determiner determines a failure using a sum of squares or asquare root of sum of squares of the first detection signal and thesecond detection signal.
 10. The angle detection device according toclaim 1, wherein at least one of the first detection signal or thesecond detection signal is multiplied by a correction coefficient basedon an amplitude ratio, so as to be corrected.
 11. The angle detectiondevice according to claim 1, wherein a signal having a smaller amplitudeout of the first detection signal and the second detection signal ismultiplied by a correction coefficient that is not less than 1 based onan amplitude ratio, so as to be corrected.
 12. The angle detectiondevice according to claim 1, wherein the phase difference between thefirst sine signal and the second sine signal is not less than π/3 andnot greater than ⅔π.
 13. The angle detection device according to claim1, wherein the phase difference between the first sine signal and thesecond sine signal is π/2.
 14. The angle detection device according toclaim 1, wherein the phase difference between the first sine signal andthe second sine signal is π/3 or ⅔π.
 15. The angle detection deviceaccording to claim 1, wherein the angle detector is any one of aresolver, a sensor using magnetic resistance, an encoder, or a Hallelement.